Protractor



A. R. cREAxN PROTRACTOR 2 SheetS-Sheet l Filed July` 19' 1947 H ammPatented Aug. 2, 1949 UNITED STATES `PATENT OFFICE PROTRACTOR Alfred R.Creain, Covingtomlly. Application July' 19, 1947,' Serial No. 762,157

8 Claims. (Cl. 33-91) The present invention relates 4to a -protractorfor use 4in connection Vwith a lstraight edge by draftsman and the like.

An object of the invention is to provide a protractor device affordingaccurate layout of angles from a straight edge.

Another object of vthe invention is to provide a device .of thischaracter lthat is capable of rapid adjustment to simultaneously attainselected equal angles on either side of a vertical center line.

Still another object ofthe invention is to provide a protractor enablingthe layout of lines that are at right angles to each other and onopposite sides'of a vertical center line.

A further object of the invention is to provide for the simultaneouslayout of'selected equal angles from the vertical and the horizontal sothat the complements of said angles are likewise available.

A still further object ofthe invention is to provide a device vaffordinga layout of lines closer to a straight edge thanv that afforded by otheravailable instruments of similar nature.

It is a special object of the invention to provide an instrument whichis easily set to attain accurate angle measurements together with theop'- posite and the complement thereof without necessity of mathematicalcalculation and a new adjustment based on such mathematical calculation.

These and other objects are attained by the means described herein anddisclosed in the accompanying drawings, in which:

Fig. 1 is a fragmental top p lanV view'of aprotractor of the invention.

Fig. 2 is a bottom end elevational view of the device .of Fig. l.

Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. 2, andshowing in'full and dotted lines the limits of adjustment of thestraight edges.

Fig. 4 is a cross-sectional View taken on line 4 4 of Fig. 1.

Fig. 5 is a cross-sectional view taken on li'ne 5-5 of Fig. 1.

Fig. 6 is a crosssec.tiona1 view-taken on line E-6 of Fig. 1.

Fig. '7 is a cross-sectional view taken'on line l--l of Fig. 1.

Fig. 8 is a cross-sectional View taken von line 8--8 of Fig. 1.

The protractor of the' invention comprises'a relatively flat hollowhousing 'I'I'I havinga straight edge II adapted to rest against the'straight edge (not shown) which is used with the drawing board. Withinthe hollow housing I0 are contained co-operating elements (hereafterdescribed) whereby associated straight edges I2, I3, Ill, and I5 aresimultaneously moved toward univform angles of adjustment about twopivot studs 'I6 and Il which are suitably journaled in the upper andlower parts ofthe housing I0.

Referring now to Figs. 1, 3 and 8 it Vwill be seen that stud I6 has anintermediate shoulder or angular flange I8 below which is a gear segmentI9 journaled on the stud between the bottom of housing I il and flangeI8. Segment I9 has an integral arm 2) t0 which straight edge I3 issecured in suitable fashion as lby screws 2|. It will be noted furtherthat another gear segment 22 is mounted for rotation on the stud Iiibetween the top of ange I3 and the upper half vof housing ID. Segment 22has an integral arm 23, to the bottom of which the straight edge I2 issecured by means of screws such as 2 I. The gear segments VI9 and 22 arerecessed on adjacent faces and coiled spring 24 is disposed in the spacebetween the segments and surrounding ilange I8. As can be best seen inFigs. 3 and 4 spring 24 has its respective opposite ends turned upwardlyand downwardly from the plane of the coil and anchored to the segments I9 and 22 respectively by entering the ends 26 and 2l into perforationsin said segments. In a generally similar arrangement stud I1 has anintegral shoulder 28 and serves as a pivotal support for an upper gearsegment 29 and a lower gear segment 30 the respective segments havingarms 3l and 32 to which the straight edges I4 and I5 respectively aresecured. A pinion 33 is journaled on a stud 34and meshes with the uppergear segments 29 and 22 so that arms 23 and 3l carrying straight edgesI2 and I4 are moved simultaneously and in the same direction whenevermovement is imparted to either of them. It will be noted that thestraight edges I2 and I4 are at right angles to each other.

In a similar fashion the lower gear segments I9 and 30 are arranged tomesh with a pinion .35 which is journaled on a stud 36 having anupwardly projecting integral screw stud 3l. These Vlower gear segmentsI9 and 30 carryarms 29 and 32 respectively to which straight edges I3Vand l5 are attached. Thus the movement otarm I3 or I5 will impart tothe remaining arm a like motion and in the same direction. It should benow observed that pinion 35 also meshes with pinion 33; which latterpinion meshes with the segment carrying the arms to which straight edgesI2 and VIII are attached.` Hence the movement .of straight edge I5, forexample, from the full line position in Fig. 3 to the dotted lineposition thereof will impart a precisely corresponding movement ofstraight edge I3 from its full line position to its dotted lineposition. This much .of the movement is aiorded through segment 3U,pinion 35, and segment I9. This movement of pinion 35 will ailord acorresponding movement of pinion 33 in the opposite direction so thatstraight edges I2 and I4 will be simultaneously moved from the full lineposition to the dotted line position.

The initial disposition of arms 20 and 32 at right angles to each otherand arms 23 and 3| at right angles to each other is maintained by theaction of the springs 24 in their respective sets of superposedsegments. The springs are at all times in opposition to any play in theteeth of the pinions and segments.

A generally quadrant shaped sheet metal plate 38 has a flatwise slidingmovement on the top of housing I and it is fixed with the stud 34 so asto move therewith as the arms carrying the straight edges are moved. Themounting may be effected by means of a washer 39 which is slightlysunken in a suitable annular recess in the top of plate 38, said washerand plate being secured to the top of stud 34 by means of a screw 4Uwhich is threadedly entered into a tapped hole in said stud. A pin 4I ispassed eccentrically through the washer and plate and into said studbefore the screw 40 is attached.

Plate 38 has an arcuate slot 42 formed on a radius having stud 34 as acenter and located so as to enable the screw stud 31 on the top of stud36 to extend through the slot and permit movement of the plate 38. Athreaded cap or nut 43 on screw 31 may be tightened to bind the plate 33against movement over the top of the housing I0 and it thus serves tohold the straight edge scales I2, I3, I4 and I5 in adjusted positionswhen desired.

The edge of plate 33 is grooved and it rides on a concentric tongue orrib 44 of an index plate 45.

The matching edges of the relatively moveable plates 38 and 45 areprovided with graduated scales for the purpose of enabling rapid andaccurate adjustments of the'straight edges to select'ed angles. A 90 arcon the edge of plate 38 is divided to provide indexing marksrepresentative of forty-five degrees of adjustment and at both ends afew additional like graduations are provided. The graduations are markedwith a double set of iigures which indicate respectively 0 to 45 and 45to 90. Y'I'he fixed plate 45 has a zero index line at its center and isgraduated on opposite sides thereof with subdivisions Yrepresentingminutes for plus or minus reading and adjustment. The effect/of themoveable angle scale and the fixed minutes scale is substantially thatof a Vernier adjustment.Y v Y It will be understood that thespecicstructuralY details of the device as illustrated may be subject tomodication within the spirit of-the invention and the scope of theappended claims.

Ihe operation of the device will be readily apparent to thoseVconversant with the graphic mechanical arts. It will be noted that thesprings E4 operate to resist play in the meshingy engagement of theseveral segments and pinions and hence accurate adjustments4 of thestraight edges to selected angles mayY be reliedupon. In use Vthestraight bottom Vedge'll lofthe housing would be. placedv against thestraightedge onthe draw- 2 associated straight edges.

ing board. The ends of the straight edges I2, I3, I4 and I5 adjacenthousing Ill will be noted to be at all times closer to the straight edgeon the drawing board than is possible with the selectively adjustabledevices of this general character now available. When an adjustment to agiven angle is to be made with one side of one of the straight edges,the cap or nut 43 is loosened and the selected adjustable straight edgee. g. I5 is merely moved to the desired angle. In moving one straightedge I5 a given number of degrees away from the horizontal, thecorresponding straight edge I2 moves a like number of degrees from thehorizontal on the opposite side of the vertical center line. At the sametime straight edges I3 and I4 move away from the vertical center line inopposite directions so that they assume angles which are the complementto that to which the associated straight edge was set. Furthermorestraight edges I2 and I4 will also remain at right angles to each otherthroughout the full range of adjustment and straight edges I3 and I5which are right angles als-o will remain at right angles to each other.The Vernier adjustment enables the user to avoid error of adjustmentaccording to an incorrect mathematical calculation as Well as themechanical error ofadjustment to a mathematical calculation Vwhichsometimes occurs, particularly where it is desired to lay out an anglein degrees and minutes at one place and to also lay out the complementof said angle, possibly as an opposite complement. For example, if thestraight edge I3 is to be set at 70 20 it would be moved until thecharacter lll on the plate 38 yregisters with the 0 on plate 45 then itvWould be shifted further until the 20 mark matches with the nextsucceeding mark on plate 38.Y The cap 43 may then be tightened to bindthe parts against movement, whereupon it would be found that thestraight edge I4 has been moved to an opposite angle of 70 20f and thestraight edges I2 and I5 Will have assumed opposite angles of 19 40',which are the complement to the settings of the The layout of beveledgear'trainsv in machine drawings will be appreciated as a simple exampleof the Yeiectiveness of the protractor of the present invention bothasto accuracy and as to time saving.

What is claimed ls: Y

1. In a protractor the combination of a at hollow housing, a pairofpivot studs in the housing in spaced parallel relation, a pairofsuperposed gear segments on each stud, a pair of straight. edgemembersdisposed at .right angles to each other and mounted respectively formovement with the lower gear segments, a pinion intermediate and meshingwith said lower gear segments, a second pair of straight edge .membersdisposed .atrightangles to each other and mounted respectively formovement withltheupper gear segments, and a second pinion intermediateYand. meshing with the uppergearsegments and also meshing with the first.mentioned pinion. -V Y. -f Y 2. In a protractor the combination ofa flatyhollow housing, a pair of pivot studs 'in the. houstermediate andmeshing-with said lower l gear .segmentaasecondpair ofstraight edgemembers 'disposedat right .angles ,toeach other and,

mounted respectively for movement with the upper gear segments, and asecond pinion intermediate and meshing with the upper gear segments andalso meshing with the first mentioned pinion, one straight edge of eachof said pairs of straight edges being disposed at all times intermediatethe straight edges of the other pair.

3. In a protractor the combination of a flat hollow housing, a pair ofpivot studs in the housing in spaced parallel relation, a pair ofsuperposed gear segments on each stud, a pair of straight edge membersdisposed at right angles to each other and mounted respectively formovement with the lower gear segments, a pinion intermediate and meshingwith said lower gear segments, a second pair of straight edge membersdisposed at right angles to each other and mounted respectively formovement with the upper gear segments, a second pinion intermediate andmeshing with the upper gear segments and also meshing with the iirstmentioned pinion, and externally disposed means for securing one of saidpinions against movement for retaining all of the segments and theassociated straight edges in adjusted positions.

4. In a protractor the combination of a flathollow housing, a pair ofpivot studs in the housing in spaced parallel relation, a pair ofsuperposed gear segments on each stud, a pair of straight edge membersdisposed at right angles to each other and mounted respectively formovement with the lower gear segments, a pinion intermediate and meshingwith said lower gear segments, a second pair of straight edge membersdisposed at right angles to each other and mounted respectively formovement with the upper gear segments, a second pinion intermediate andmeshing with the upper gear segments and also meshing with the firstmentioned pinion. a quadrant shaped plate fixed for movement with one ofsaid pinions and slidable over the exterior of the housing, said platehaving graduations denoting degrees of angular adjustment of the Segnments and associated straight edges; and a xed plate on the housinghaving at least one indexing line.

5. In a protractor the combination with a pair of spaced apart parallelstuds, of a lower gear segment on each stud, an upper gear segment oneach stud, a pair of pinions meshing with each other, one of saidpinions meshing with the lower segments, the other of said pinionsmeshing with the upper segments, straight edges iixed to the respectivelower segments and disposed at right angles to each other, straightedges xed to the respective upper segments and disposed at right anglesto each other, and spring members yieldably urging the companion upperand lower segments in opposite directions.

6. A protractor comprising a pair of parallel studs, straight edgemembers having toothed segmental ends mounted for movement about saidstuds as centers, said members disposed at right angles to each other, apinion meshing at opposite sides with the respective toothed segmentalends, and means yieldably urging the segments into toothed drivingengagement with the pinion in one common direction, and yieldablyresisting toothed driving engagement thereof with the pinion in theopposite direction.

'7. A protractor comprising a housing having a straight bottom edge andprovided with slots extending longitudinally through the remainingedges, two spaced apart pairs of sup-erposed concentric gear segmentsrotatably mounted within said housing and each having a tangential armextending through an edge slot in the casing, and a pair of mutuallymeshing pinions rotatably mounted intermediate said spaced pairs of gearsegments and meshing respectively with the upper gear segments and thelower gear segments respectively of said spaced pairs of gear segments,the arms of the lower gear segments being disposed at ninety degrees toeach other and the arms of the upper gear segments being disposed atninety degrees to each other, the said pinions retaining said ninetydegree angularity of said arms during rotary movement of the meshingpinions and segments, and serving to simultaneously move the arms of thelower gear segments in one direction and the arms of the upper gearsegments in the opposite direction.

8. A protractor comprising a housing having a straight bottom edge andprovided with slots extending longitudinally through the remainingedges, two spaced apart pairs of superposed concentric gear segmentsrotatably mounted Within said housing and each having a tangential armextending through an edge slot in the casing, a pair of mutually meshingpinions rotatably mounted intermediate said spaced pairs of gearsegments and meshing respectively with the upper gear segments and thelower gear segments respectively of said spaced pairs of gear segments,the arms of the lower gear segments being disposed at ninety degrees toeach other and the arms of the upper gear segments being disposed atninety degrees to each other, the said pinions retaining said ninetydegree angularity of said arms during rotary movement of the meshingpinions and segments, and serving to simultaneously move the arms of thelower gear segments in one direction and the arms of the upper gearsegments in the opposite direction, and spring means urging each pair ofsuperposed gear segments in opposite directions and into toothed drivingAengagement with the pinion meshing therewith.

ALFRED R. CREAIN.

REFERENCES CITED UNI IE D STATES PATENTS Name Date Wall et al Feb. 13,1917 Number

